The invention concerns an optical multiple circuit breaker according to the preamble of claim 1.
In the field of optical information technology, optical switches are gaining importance for optional connection of optical information channels both together and with local networks and end users. In particular, there is a need for optical multiple circuit breakers of compact and simple construction which allow coupling of optical components or beam waveguides into existing beam waveguide arrangements.
Mechanical matrix switches are known in which mirrors or prisms are moved with high precision. Switches based on mirror or prism arrangements require a very stable and precise structure. The required precision is generally associated with a very high technical complexity.
As well as optical switch elements in which the micro-optical components are moved with high precision, optical switch elements are also known which work on a switch principle which does not require the movement of micro-optical components.
GB 1 494 150 describes an optical switch element in a beam waveguide in which an interface receiving incident light is switched between a state of total reflection and transmission. The known optical switches have a narrow gap in the beam waveguide core. The gap forms a flat interface between a medium with higher refractive index, i.e. the material of the beam waveguide core, and a medium of lower refractive index, i.e. a gaseous substance in the gap, so that light hitting the interface obliquely, guided along the beam waveguide, is totally reflected at the interface in the direction of an adjacent beam waveguide. To switch to the transmitting state in which the light hitting the interface retains its direction of propagation, a fluid with a refractive index which matches that of the material of the core of the beam waveguide is introduced into the gap. A storage vessel with a heating device attached to the beam waveguide provided as a device for optional introduction of the substance in its liquid or gaseous phase. By thermal expansion, the fluid is pressed into the slot penetrating through the casing layer into the core layer of the beam waveguide. In another design form, the liquid substance in the slot is brought to the gaseous phase by heating.
The complex production of the known switch is a disadvantage. Furthermore the known switch has a high optical attenuation, as the light beam emerging divergent from the beam waveguide is not guided in the area of the slot. Therefore in the transmitting switched state, part can be coupled over to the adjacent beam waveguide, which leads to a high crosstalk. Production of an optical multiple circuit breaker with several inputs and outputs required a correspondingly high number of these known switch elements and would therefore be very costly to implement.
IEEE Transactions on Components, Packaging and Manufacturing Technology-Part B, Vol. 18, No. 2, May 1995, Pages 241-244, discloses an optical multiple circuit breaker according to the preamble of claim 1.
One decisive disadvantage of this optical multiple circuit breaker is the restriction to one set of N optical inputs lying in one plane and aligned parallel to each other. There is no freedom of design with regard to the arrangement of optical inputs and outputs because of the arrangement of the recesses with reflective surfaces in one plane and their parallel alignment. Thus with this optical multiple circuit breaker, use of coupling of an optical assembly or a local glass fiber network to existing optical data lines for example is simply not possible.
Another disadvantage is the high number of switch elements. The known optical multiple circuit breaker with N optical inputs has Nxc3x97N individual switch elements which must be controlled individually by robots for switching between the reflective and the transmitting switched state. Simultaneous and hence rapid switching of all switch elements is not therefore feasible.
Because of the multiplicity of the switch element arranged in one plane, the known optical multiple circuit breaker has relatively long optical path lengths so that to avoid a high optical attenuation and crosstalk, a light guide is provided by means of integral waveguides.
On the basis of the state of the art described, the task of the invention is to prepare an optical multiple circuit breaker with which optical inputs can be switched to optical outputs so that for example an optical assembly or a local glass fiber network can be coupled onto existing optical data lines without problems, and which allows a simple and hence fast switching between the reflective and transmitting switched states, and which has a compact structure and hence short optical path lengths.
The task is solved according to the invention with the features given in claim 1 and in claim 3. The dependent claims concern advantageous designs of the invention.
The optical multiple circuit breaker according to claim 1 has 2xc3x97N optical inputs E1(n) and E2(n) and 2xc3x97N optical outputs A1(n) and A2(n), where n is an index from 2 to N, with N greater than or equal to 2. By optical reflection or transmission at two surfaces, thus 2xc3x97N light beams from the 2xc3x97N optical inputs can be switched to the 2xc3x97N optical outputs. To form these two surfaces, the base body of the optical multiple circuit breaker has a maximum of two recesses. In the transmitting switched state, the recesses are filled with a substance with a refractive index corresponding approximately to that of the transparent base body material. Thus the transmission of the incident light beams from the N first optical inputs E1(n) to the N second optical outputs A2(n) is possible. In the reflective switched state, the recesses are filled with a substance with a lower refractive index. Two surfaces of the recesses are formed and arranged in the beam path so that in the reflective switched state, the first surface reflects the incident N light beams from the N first optical inputs E1(n) essentially to the N first optical outputs A1(n), whereas the second surface reflects the incident N light beams from the N second optical inputs E2(n) essentially to the N second optical outputs A2(n). Essentially the reflections are total reflections at the interface of a medium of higher refractive index, i.e. the base body, to a medium of lower refractive index, i.e. the substance of lower refractive index in the recess. At least one device fills the recesses optionally with the substance of higher or the substance of lower refractive index.
According to one design form, the two surfaces involved in the optional reflection or transmission are arranged parallel to each other so that the N second optical inputs E2(n) and the N first optical outputs A1(n) lie on opposite sides of the base body. For this the base body can have two recesses or one recess, for example with a parallelo-gram-shaped cross-section.
The optical multiple circuit breaker according to the invention according to claim 3, like the optical multiple circuit breaker in claim 1, has 2xc3x97N optical inputs E1(n) and E2(n) and 2xc3x97N optical outputs A1(n) and A2(n), where n however is an index from 1 to N with N greater than or equal to 1. By optional reflection or transmission at two surfaces formed by a maximum of two recesses in the base body, here 2xc3x97N light beams from the 2xc3x97N optical inputs are switched to the 2xc3x97N optical outputs. In comparison with the optical multiple circuit breaker according to claim 1, the base body of this switch has two additional surfaces formed and arranged in the beam path of the light beam so that in the transmitting switched state by reflection at these additional surfaces the N second optical inputs E2(n) are optically connected to the N first optical outputs A1(n). As in the optical multiple circuit breaker to claim 1, here too in the transmitting switched state the N first optical inputs E1(n) are optically connected with the N second optical outputs A2(n), and in the reflective switched state the N first and the N second optical inputs E1(n) and E2(n) are optically connected with the N first and N second optical outputs A1(n) and A2(n) respectively.
Preferably one of the two additional surfaces of the base body of the optical multiple circuit breaker to claim 3 lies opposite the N first optical outputs A1(n) and the other additional surface lies opposite the N second optical inputs E2(n).
Advantageously the two additional surfaces are arranged at an angle of 70xc2x0 to 110xc2x0 to each other. In the transmitting switched state, the light beams from the N second optical inputs E2(n), transmitted by the recess, are diverted by reflection at these two additional surfaces to the N first optical outputs A1(n).
The two additional surfaces can correspond to external surfaces of the base body or be formed by one or more additional recesses in the base body.
Preferably the light beams hitting these additional surfaces are totally reflected. For this, these surfaces form interfaces between a medium of higher refractive index i.e. the material of the transparent base body part, and a medium of lower refractive index, i.e. the outer environment of the base body or a substance or substance mixture of lower refractive index inside the additional recesses in the base body.
The basic advantage of the optical multiple circuit breaker according to the invention is that the two interfaces responsible for the switching process are not moved, and hence no precise movements need be performed. Due to the preferred use of collimated light beams, no costly waveguide structures are necessary to guide the beam in the base body. As the beam does not divert even in the recesses involved in the switching process, the optical multiple circuit breakers according to the invention have a low optical attenuation and low crosstalk. Because of the multiple design possibilities of the recesses, optical multiple circuit breakers can be produced with different positions of inputs and outputs and with different switching possibilities. In addition, independently of the number of optical inputs, only two optically high quality surfaces are required which are formed by only maximum two recesses. In an extremely compact and simple construction therefore with the optical multiple circuit breakers according to the invention, low-cost mass production is possible.
The use of the terms xe2x80x9coptical inputxe2x80x9d and xe2x80x9coptical outputxe2x80x9d in contrast to the term xe2x80x9coptical channelxe2x80x9d serves merely to simplify the description of the optical multiple circuit breaker. Because of the reversibility of the light paths, use is possible in both directions of radiation, i.e. bi-directionally.
Preferably the optical multiple circuit breaker according to the invention is operated with free beams, i.e. light beams not guided in waveguide structures. This can for example be achieved if the light brought by means of beam waveguides is collimated or focused before the inlet to the switch itself. In principle however it is also conceivable to include in the optical multiple circuit breaker integrated optical structures to guide light, for example by means of layer or trough waveguide structures, which however requires a more complex construction of the base body.
The position of the optical inputs and outputs in the optical multiple circuit breakers is not firmly specified. For N greater than or equal to 2, an arrangement is preferred in which the N first incident light beams LS1(n) do not lie in one plane with the N second incident light beams LS2(n). Here in each case an approximately parallel arrangement of the N first and an approximately parallel arrangement of the N second optical inputs is preferred. The resulting planes of incident light beams and planes of emerging light beams can be arranged in many ways to each other depending on the geometry of the optical multiple circuit breaker used. Here preferably the optical inputs E1(n) and E2(n) are arranged such that the plane of the N first incident light beams LS1(n) lies at an angle of 70xc2x0 to 110xc2x0 to the plane of the N second incident light beams LS2(n). Advantageously here the recesses are arranged such that the angle of incidence of the light beams on a surface of a recess is around 40xc2x0, to 50xc2x0. The position of the outputs to the inputs is specified by the circumstance that the light beams transmitted from the N first optical inputs E1(n) fall on the same N second optical outputs A1(n) as the light beams reflected in the reflected switched state from the N second optical inputs E2(n).
As a result advantageously these optical multiple circuit breakers can be used in the area of optical information technology, in particular for optional connection or decoupling of optical information channels and for coupling of optical components into existing optical connections. Because of the possible rectangular arrangement of the N second optical inputs E2(n) to the N first optical inputs E1(n) for N common outputs A2(n) or also 2N common outputs A2(n) and A1(n), with the multiple switches according to the invention, in the same way as the bus systems known in micro-electronics, compact optical bus systems can be produced with orthogonal arrangements of plug cards and boards.
In a first design form of the optical multiple circuit breaker, two recesses are provided in the base body for optional reflection or transmission of light. The surfaces formed by these recesses involved in reflection lie in a preferred arrangement at an angle of approximately 70xc2x0 to 110xc2x0 to each other. However other arrangements of these surfaces to each other are conceivable.
Also with the geometry of the cross-section of a recess in the plane of the beam path of a light beam, many designs are possible depending on the method of desired beam guide and the production process used. In the two simplest cases, the cross-section essentially takes the form of a rectangle or triangle.
In a second preferred design form of the optical multiple circuit breaker, only one recess is contained in the base body which forms the two surfaces on which light is either reflected or transmitted. In a preferred design form, these two surfaces lie at an angle of approximately 70xc2x0 to 110xc2x0 to each other. Here too however other arrangements of these surfaces to each other are conceivable. Examples of cross-section geometries of the recess are a triangular and a trapezoid cross-section. If the recess is formed by a gap, for example a V-shaped or trough-shaped cross-section of the recess is possible.
Preferably in the approximately orthogonal arrangement of the reflective surfaces, the N second optical inputs E2(n) and the N first optical outputs A1(n) lie on the same side of the base body.
The base body with which the optical multiple circuit breaker according to the invention is achieved ran consist of one or more parts, where the recesses are advantageously closed at their ends preferably by cover plates.
Surfaces at which reflections occur should, to avoid scatter, have a sufficiently high optical quality. Surfaces through which light is merely transmitted need not have a high optical surface quality as in the transmitting switched state they are in contact with the substance of higher refractive index.
The base body should, at least in the beam path, consist of a material transparent in the wavelength range used. It can be made from just one or from various transparent materials. Suitable materials may for example be transparent polymers such as where applicable fluoridated polymethylmeth-acrylate (PMAA), glass or transparent materials produced in a sol-gel process.
As well as the recesses described, the base body can also have one or more further recesses. These can be formed and also structured so that they are suitable to receive and hold individual beam waveguides or waveguides grouped into fiber bundles. In addition advantageously devices can be integrated to hold fiber plugs to allow simple connection with the optical input and output beam waveguides.
Such additional recesses can also hold in the base body optical elements such as spherical lenses, microlenses, GRIN lenses and/or cylindrical lenses, for collimation and/or focusing in particular of the light beams emerging divergent from the beam waveguides. It is also conceivable to hold for example linear microlens fields for bundling of light beams of several optical channels.
It is however also conceivable to form one or more additional recesses and arrange these in the beam path so that light beams penetrating these are bundled. As well as the shape of these recesses, by varying the ratio of refractive indices between the transparent base body part and the substance or substance mixture inside these additional recesses, the optical properties of these recesses serving as optical components can be adjusted.
In addition, the two surfaces of the recess or the two recesses via which optional transmission or reflection is achieved, and/or the two additional surfaces of the base body can be formed, for example as a cylindrical lens or microlons array, such that in the reflective switched state light is reflected and bundled. It is also conceivable to set the refractive index of the substance of higher refractive index in relation to the refractive index of the transparent base body material and to form the recess or recesses so that the transmitted light is bundled.
The substance or substance mixture of lower refractive index present in the recess or two recesses in the reflective switched state can for example be an inert gas such as argon or even air. The substance of higher refractive index can be a fluid or fluid mixture. Thus to adapt the refractive index to PMMA, a mixture of decalin and tetralin is suitable. As a substance with lower refractive index, a fluid which preferably does not mix with the substance of higher refractive index could also be used.
It may be advantageous, at least for the surfaces of the recesses involved in reflection, to subject these to additional treatment, for example chemical or plasma-chemical, or coat these with one or more suitable materials in order to change their wettability. In this connection, a fine structuring of the relevant surfaces can be advantageous.
As a device for optional filling of the recess involved in reflection and transmission, a fluid reservoir of variable volume can be provided, connected with the recess and located for example outside this. A force acting on the fluid reservoir from the outside, for example an electric piezo element, a thermoelectric element or an electromagnetic arrangement, now presses the substance of higher refractive index or substance of lower refractive index into the recess, whereby the optical multiple circuit breaker is switched to the transmitting or reflective switched state. If two recesses are used for optional reflection or transmission, these can have one filling device each or a common filling device connected with these.
In another design form, the substance with higher refractive index enters the recess concerned due to the thermal expansion or contraction accompanying the heating or cooling of the substance with higher and/or the substance with lower refractive index respectively. For this the device has at least one switchable heating element and/or cooling element in contact with the substance with lower and/or higher refractive index.
In a further design form, at least one micropump is provided for optional evacuation or filling of the recess.
The device for filling or evacuation of the recess with a substance with lower or higher refractive index can be fitted in the base body or outside the base body.
At least parts of the base body and/or filling device can advantageously be produced with microtechnical processes, for example the LGA process.
Several design examples of the invention are described in more detail below with reference to the drawings.